青藏高原典型流域土壤重金属分布特征及其生态风险评价

青藏高原属于环境极端脆弱区和人类活动敏感区,近年来在该区域检测到越来越多的人为干扰.本研究基于甘南"一江三河"和西藏"一江两河"两个流域,分析了Cr、Ni、Cu、Zn、As、Cd和Pb这7种重金属的空间分布关系及其生态风险.结果表明,甘南"一江三河"流域7种重金属的空间分布呈东部高西部低的特点,平均含量均超过青藏高原背景值,以Cd （4.50倍）和As （2.83倍）较显著,Cd和Pb的高值主要分布在水域、城镇及农村居民用地和工交建设用地;西藏"一江两河"流域7种重金属的空间分布呈沿江一线重金属含量较低、高海拔地区重金属含量较高的特点,Ni、Zn、As和Cd的平均含量超过青藏高原背景值,以Cd （3.13倍）较显著,Cd的高值主要分布在水域覆盖区.地累积指数法和潜在生态风险指数法表明,在甘南"一江三河"流域以As和Cd的污染程度较高,且在水域覆盖区潜在生态风险最高;西藏"一江两河"流域以Cd的污染程度较高,水域覆盖区潜在生态风险最高.本研究对青藏高原不同土地利用方式下土壤环境保护和可持续开发利用具有指导意义.

Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals in Typical Watersheds of the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is an extremely vulnerable area that is sensitive to human activities. In recent years, more and more human disturbances have been detected in this area. This study analyzed the spatial distribution and ecological risks of 7 heavy metals (Cr, Ni, Cu, Zn, As, Cd, and Pb) in two regions, namely the Bailong River and Yellow River and their two tributaries (BY region) in Gannan and the Yarlung Zangbo River and its two tributaries (YZ region) in Tibet. In terms of spatial distribution, concentrations of the seven heavy metals were higher in the east and lower in the west of the BY region. The average concentrations all exceeded the background value of the Qinghai-Tibet Plateau, especially for Cd (4.50 times) and As (2.83 times). High Pb concentrations were mainly found in water, urban and rural residential land, and industrial and construction land. In the YZ region, heavy metal concentrations were lower along the river, while high-altitude areas exhibited higher heavy metal concentrations. The average concentrations of Ni, Zn, As, and Cd exceeded the background values of the Qinghai-Tibet Plateau, especially that of Cd (3.13 times), which mostly exhibited high values in water coverage areas. The geo-accumulation index method and the potential ecological risk index method show that the degree of As and Cd pollution was relatively high in the BY region in Gannan, with the greatest potential ecological risk occurring in the water coverage area. In the YZ region in Tibet, the degree of Cd pollution was high, with the highest potential ecological risk also occurring in the water coverage area. This study provides significant guidance for the environmental protection, sustainable development, and utilization of soil under different types of land use in the Qinghai-Tibet Plateau.